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Urbanization strongly associated with allergic illness

Published online: January 18, 2018

The prevalence of asthma is increasing rapidly in low- and middle-income countries (LMICs) even as it declines in high-income countries. Allergic disorders, including asthma, rhinitis, and eczema, contribute greatly to morbidity, mortality, and economic burden. Urbanization has been shown to be correlated to allergic disorders in various settings, representing a variety of established risk factors: poorer nutrition, reduced activity, and traffic or industry-related air pollution. The prevalence of allergic disorders is expected to rise as rural to urban migration rapidly increases in sub-Saharan Africa. Representative of this transition, Uganda has experienced massive urban growth over the past four decades, largely due to unplanned urban sprawl. To date, there has been only one population-based study of respiratory health among adults in Uganda, which focused on Chronic Obstructive Pulmonary Disease (COPD). Data on allergic illnesses are necessary in order to inform public health policy and medical treatment in Uganda.

In a recently published article in The Journal of Allergy and Clinical Immunology: In Practice, Morgan and colleagues present an analysis of baseline data from the Lung Function in Nakaseke and Kampala (LiNK) Study: a population-based longitudinal cohort of adults in Uganda. They estimated the prevalence, risk factors, and attributable risk of asthma and allergic disorders between rural and urban settings. A total of 1,769 adult participants were randomly sampled from Kampala (urban) and Nakaseke (rural), wherein they were administered comprehensive surveys covering demographic information, health history, and respiratory symptoms before completing lung function testing via spirometry. Asthma was defined as previous physician’s diagnosis, recent use of medications, or recent wheeze. Rhinitis and eczema were defined by self-reported symptoms.

The authors found an age-adjusted prevalence of asthma of 6.8%, which was higher in the urban site (9.8%) than the rural site (4.3%, p<0.001). There was a sizable prevalence of rhinitis (11.9%) and eczema (8.2%) as well. Urbanization was most strongly associated with allergic illness. Asthma was associated with increased odds of life impairment and deficits in spirometry, associations that may be worse among those who have comorbid eczema. Those in the rural site who reported recent wheeze sought care and were diagnosed with asthma at a lower rate than those in the urban site.

In the first large, population-based study of adults across the urban-rural gradient in Uganda, a high prevalence of allergic disorders was found, largely driven by urbanization. Further, local patterns in care-seeking behavior were seen that may explain a portion of the discrepancy in asthma diagnosis and treatment in rural communities. As urban migration continues in sub-Saharan Africa, it is important that health systems in the region address the growing burden of allergic illness.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.